1. Field of the Invention
The present invention relates generally to optoelectronic detectors and more specifically to fiber optic detectors for detecting the presence of a chemical reaction.
2. Description of the Prior Art
Chemical reactions are critical to many processes in industry. Often the chemicals involved are hazardous and/or must be used at high pressures in sealed containers. When the reactions take place in the sealed containers, the human operator cannot directly determine if the chemical reaction is complete. The operator must estimate when the reaction has been completed and new chemicals added to replace the exhausted reactants.
One example involves the purification of gases. Many industries, such as the semiconductor industry, require high purity gases. To obtain this high purity, the gases must be passed through a chemical purifier which removes unwanted gases, moisture and other impurities. The chemical purifier contains a chemical resin through which the gas is passed. The resin is usually in the form of small one millimeter size pellets.
As the gas passes through the container, the resin reacts with and absorbs the unwanted gases, moisture and impurities. The resin near the entrance opening in the purifier reacts and is exhausted first. Thereafter, successive layers of resin are used up, and the boundary between the reacted resin and the unreacted resin moves down the container like a wave until all of the resin is exhausted. The container must then be replenished with fresh resin.
In order to maintain a constant high purity level of gas, the resin in the purifier must be replaced before it is exhausted. However, the high pressures and hazardous gases make direct inspection of the resin impossible. In addition, due to variables, such as the flow rate and the initial level of impurity of the gas, it is difficult to estimate when to replace the resin. Operators either replace the resin long before it is fully spent or wait until a sharp increase in the level of gas impurity is noticed.
Thus, there is a need for a means to automatically determine when the resin nears exhaustion so that the resin may be replaced and the purity level of the gas in the system maintained.